Conventional sonar systems traditionally consist of a plurality of discrete transducers aligned in linear, curvilinear, or planar arrays. Directional resolution is accomplished through analog or digital electronics by beam steering. Such systems usually require a large number of discrete transducers and electronics which includes signal conditioning amplifiers and digital computers. These are complex systems which are large, heavy, difficult to maintain and calibrate, expensive, and require significant electrical power.
One recent approach proposes an alternative means for obtaining high resolution without steering using derivative-matched spatially shaded sensing apertures consisting of a number of discrete sensors. However, this implementation introduces directional ambiguities and/or implicit bandwidth limitations to prevent spatial aliasing. In addition, a large number of discrete sensors is required which continues the problem of large size, weight, expense, maintenance and calibration.
More recently in the related case cited above a wideband, derivative-matched, continuous aperture acoustic sensing system was achieved by erecting the derivative-matched shading, physically, in the transducer with two sensor areas, one or which possesses a shading which is the spatial derivative of the other and with the two sensor areas superimposed and coincident along the sensing axis.
Although such derivative-matched transducers work well for generally flat surfaces, many applications require mounting on curved surfaces such as the cylindrical or elliptical surfaces of ships and underwater devices. Often sonobuoy probes and autonomous undersea vehicles (AUV's) have constrained platforms, i.e., limited space for instruments, so there is little room to accommodate "flat" transducers although there is mounting space available on the curved surfaces of such devices.